Coded track circuit signaling system



July 2, 1946. -r. J. JUDGE CODED TRACK CIRCUIT SIGNALING SYSTEM 1941 14Sheets-Shae}. 1-

Filed Feb. 14

INVENTO y 1946. T. J. JUDGE CODED TRACK CIRCUIT SIGNALING SYSTEM FiledFeb. 14, 1941' 14 Sheets-Shee t 2 O I wylg wl ATroimEY INVENT NE J XEKEN? \ I l l I I I I I a 0mm 14 Sheets-Sheet 3 N. mi W92 Tu I T. J.JUDGE Filed Feb; 14, 1941 Haw J V 5 CODED TRACK CIRCUIT SIGNALING SYSTEMv I rmw I I l l 54 3 3 July 2, 1946.

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T. J. JUDGE CODED TRACK CIRCUIT SIGNALING SYSTEM Filed Feb. 14. 1:941 14Sheets-Sheet 5 y 2, 1946- 'f T. J. JUDGE v CODED TRACK CfRCUIT SIGNALINGSYSTEM l4 Sheets-Sheet 6 so? NE? NW@ im m 5% infi NHQQL m Filed Feb. 14,1941 RHT INVENTOR 7152 July 2, 1946. T. J. JUDGE I v CODED TRACK CIRCUITSIGNALING SYSTEM 14 Sheets-Sheet 7 INVENTOR4I BY MW W ATTORNEY FiledFeb. 14, 1941 July 2, 1946.

T. J. JUDGE CODED TRACK CIRCUIT SI GNAL ING SYSTEM "Filed Feb: 14, 194114 Sheets-Sheet 8 N mam 3 I 165. mc En 296 :6 mnm .QWwE

"Jul 2, 1945.]

1-,,1. JUDGE CODED TRACK CIRCUIT SIGNALING S YSTEM Filed Feb. 14, 194114 Sheets-Sheet 9 NTO ATTORNEY ou qr fl July 2, 1946. T. J. JUDGECODEDTRACKflIiiCUIT S IGNALIN G SYSTEM 14 Sheets-Sheet 10 INVENTOR fATTORNIEY J BY. LU

Filed Feb. 14, 1941 y 1946- T. J. JUDGE- CODED TRACK CIRCUIT SI GNALING'SYSTEM 14 Sheds-Sheet 11 Filed Feb. 14, 1941 ATTORN'EY m FY S 14Sheets-Sheet l5 T. J. JUDGE Filed Feb. 14, 1941 July 2, 1946.

CODED TRACK CIRCUIT SIGNALING SYSTEM July 2, 1946. T. J. JUDGE CODEDTRACK CIRCUIT SIGNALING SYSTEM 14 Sheets-Sheet 14 1 wm fiI. m MW Tmwnn la RE 1 .QGMMWJ N QW m m H. @m w WBQL B m 3 I F ATTORNEY Patented July 2,1946 Thomas J. Judge, Rochester, N."Y., assignor to General RailwaySignal Company,'Rochester,-

Application February 14, 1941, Serial No. 378,961

31 Claims. (01. are-33y The present invention relates to railway sig- Wnaling systems and more particularly to a rail-'- way signaling systemof the absolute-permissiveblock type.

For economic reasons it is important to keep the number of line wiresalong the railway track to a low number. In accordance with the pres entinvention it is proposed to obtain all of the facilities and speed ofoperation of the signal controls heretofore enjoyed in railwaysignalused through'the passing siding. In order to obtain thesefacilities it is proposed in accordance with the present invention toemploy only twoline line wires extending from each signal location tothe next signal location through both single track sections and passingsidings, and to employ a relay or other electro-responsive device ateach end of such pair of line wires to afford double use of these line'wires. It is proposed to employ a source of current at eachend of suchpair of line wires and to provide synchronously operated contacts onthese electro+ responsive devices near the end of each of the pair ofline wires, for the purpose of at one instant connecting the relay atone end'of these ing systems of the absolute-permissive-blocl;

- track section.

line wires to the. source at the other end and Another feature of thepresent invention resides in the employment of an inverse code sometimescalled an' ofi code for the purpose of transmittingadditionalinformation over a track circuit in the direction from the track relayend toward the track batt'ry'end thereof; Another feature of the presentinvention resides in the provision of signaling circuits whereby thepres-' ence ofy-a-train on one passingsiding is manifasted byfthedisplayof a caution signal at the next passing siding in advance of 5the train. This lattenfeature is -particular1y desirable where the[single track section is so short that double braking" distance is notavailablebetween two opposing intermediate signals along such singleOther objects-purposes and characteristic features of the presentinvention will in part be described hereinafter and will in part beobvious from the accompanying drawings, in which:

end constitute'one signaling system embodying l the present invention;

Fig. 2 illustrates the positions that'the contacts of the search-lightsignal assume under clear, cautionand stop :traffic conditions,respectively;

trate the signal-indicationsand their conditions of illumination when atrain occupies various points along the trackway;

"Figs. 4A, 4B; 4C, 4D and 4E illustrate .a modified form ofthe presentinvention; 7

Figs. 5A, 5B, 5C, 5D, 5E, 5F, 5G, 5H and 51 illustrate the varioussignal indications fort he system shown-in Figs. 4A; 4B, 4C, 4D, and 4EI with an eastbound train'occupying various'points for manifesting thepresence of a train in the;

posite directions over the pair of line wires above mentioned andlocated adjacent the track circuit.

along thetrack;

andGK illustrate the various signal indications and their conditionsof'illurnination when a west moving-trains make a meet o n-a passingsiding.

1 i *1 structztra Referring' to' Figs; 1A to n; inclusive, thetrackrails'fl 0 have been'shownf divided-into'sectionsby insulating joints IIf to insulate "adjacent "track sections fromeach other.

Therailway signaling system illust'rated' includes apassing side A; apassing siding B, asingle track section 0 connecting the -twopassingsidings tog game and a por'tiono'f another single track sectio'nLTheva'rious signals havebeen designated S tently closing av contact.

. 3 with a suffix number to distinguish these signals from each other,the signals Sill, vSlllA, Sll, SIZ, SIB, SM, SIT, Sl8, SIB, SI9A, S20,SZBA, S2I and S23 having been illustrated. Each of these signals mayconstitute a signal of either the semaphore type, the multiple unitlight signal 7 type, or the multiple aspect searchlight signal type, butfor convenience only the search-light type signal has been illustratedin the drawings.

This search-light type signal is preferably of a construction such asillustrated in the patent to 1 Field, No. 2,097,785, dated November 2,1937. The

polar windings of these search-light type signals have been designated Wwithasuflix number cor-y track relays being provided with a distinctiveidentifying number corresponding to the track circuit withwhich they areassociated and each of I2CPR, back contact H of the opposing directional stick relay I3S, winding of the home-distant relay l2I-ID, frontcontact 22 of the signal repeater relay MYGP and to the other terminalof said source of current. Under caution traific conditions thehome-distant relay l2I-ID is controlled through a circuit similar to theone just traced but is energized by current of negative polarity. Thiscircuit includes the same contacts as the contacts just recited exceptthat the "contacts H and 22 of the signal repeater relay MYGP assumetheir retracted position and exceptfor the fact that the front contact24 of the directional. stick relay MS is included in series in thiscircuit. The coding relay IECPR, as con- Ventionally shown, is energizedintermittently through a front contact28 of suitable codecreatthefre'maining relays being provided with a distinctive identifyingnumber corresponding to the identifying'niiniber of the signal which thehomed istant relay in question controls. Thereference characters CT. andCPR with a suitable sufiix and the relay to which it is assigneddesignate suitable code creating apparatus for intermit- Where thisletter CT or CPR has associated with it the number;75 signifies that thecontact is closed approximately seventy-five times per minute, and wherethis 1 letter CT or CPR has associated therewith the number 120signifies that its associated contact intermittently closes one hundredand. twenty times per minute. These code creating devices may be of anysuitable constructionand are preferably operated electrically andcontinuously. It is believed unnecessary to describe the circuitsassociated with all of the signalsillustrated, and

'iorconvenience the circuits. associated with the signal S12 and some ofthe circuits controlling the signal SI! only will bepdescribed. and likeparts of remaining signalcircuits willbe assigned like referencecharacters having distinctive exponents, prefixes or sufiixes.

I Referring to Figs. 13 and 1C of the drawings,

the signal Sl2 is a signal of the search-light type having a polarizedmechanism controlledby the T winding WIZ; This winding; WIZ is energizedby current. ofnormal polarity. under normal clear traiiic conditions, asillustrated. This energizing circuit extends from the terminal of. asuitable source of current through the polar contact I2 of therelayIZI-lD assuming its righthand position, the front contact [3 of thissame relay, the winding Wl2, the neutral contact {4 i 7 and the polarcontact. I5 assuming its righthandp osition and to the other terminal ofthis same source of current. This home-distantf relay IZHD is undernormal clear traflic 1" conditions, as illustrated, energized to itsright- {'T.

hand. polar position through the following circuit beginning at theterminal of a suitable source of current, front contact! 1 of the signalrepeater relay MYGP, front contact [8 of the track relay n ntact. 19 orthe-trackrepeater-re-i- *lay'l2FBP, front contact 20 of the coding relaying apparatus 'IBCT at a code rate of '75 impulses per minute. It isthus seen that the home-distant relay [2HD cannot be energized to itsleft-.

hand polar positionunless the directional stick relay for the nextsignal in advance assumes its energized position.

Itis, of course, understood that the coding. relay 'IZCPR isintermittently energized seventyfive times per minute andthat when itassumes'its energized position 'the track circuit extending fromthefsignal sm to the signal sea; is closed.

This track circuit, includes thetrack battery Bit, theapproach relayAlZT, the coding contact 25 and the track relay [2T in series. Thistrack relay [2T will of course be intermittently picked up at the ratevof seventy-five times per minute in substantial synchronism with thecoding relay IZCPR. so long as the track circuit is not occupied by atrain. 'The intermittent picking up of the track relay [21' through themedium of its front contact 26 intermittently applies energy tothe slowdropping track repeater relay IEFP so as to cause it to assume itsenergized position continuouslyand in the same manner this contact 26 asitintermittently assumes'its retracted position willl'intermittentlyapply energy to the inverse track repeater relay I2FBP through themedium of frontc'ontac'til' of the code repeater'relay IZFP, tocausethis relay I2FBP to continuously assume its energized" position. iThetrack repeater relay l2FP is. in fact an on pulse repeater relay whereastheytrack repeater relay I2FBP is anfo pulse repeater relay whichalsochecks the presence of on impulses; and therefore 6011-:

stitut'es a relay that can be up continuously only ifthe trackrelay [2Ti's'intermittently'picked up. The net resuIt is that the trackrepeaterrelay I ZFBP assumes its energized position only if the trackcircuit is intermittently energized. V

Thedi'rectional stick relay [2S is provided with a pick-up circuitincluding the 'fro-nt contact 30. r

of theapm'oach track repeater relay Ai3TP and a front contact 3P of,"the caution-clear signal,

repeater relay IZYGP. This directional stick relay IZS is also providedwith two stick circuits, one; including the back contact 3'i' 1of thesignal repeater relay I ZYGRthe other including the front contact 33 ofthe approach track repeater.

relay. A .I3.'IP, and both including. the stick contactSZl of thisdirectionalstick relay. l2'S-. "The signallrepeater relay l2YGP isnormally energized through the back. contact. 30 of the relay A1l3TP'and. the clear. contact. 33 ofthe searchlight mechanism. ofsignal S l2,and under caution traific conditions is energized in series gthroughthis back cemaetsew andthe-eontacts; are and 34 of this signal Si 2 bothassuming theletthand caution position (see. also Fig. 2 Attention is atthis time directed to Fig. 2 which illustrates the positions assumed bythe contacts 33 I and 34 under clear, caution and stop trafficconditions, respectively.

The app-roach home relay IIAHD (see Fig. 1C) is controlled by thecontacts I1 and 22 of the caution clear signal repeater relay I3YGP inexactly the same manner as the home-distant relay I2HD is controlled bythe contacts I1 and 22 of the caution-clear signal repeating relay MYGPand by the directional stick relays I35 and 14S and the track repeaterrelay IZFBP. It should, however, be noted that this approachhome-distant relay I'IAHD does not directly control a signal but doescontrol the home-distant relay llI-ID, which in turn controls signal S".The normal clear circuit for the home-distant relay HHDmay be traced asfollows: beginning at the terminal of a suitable source of current,polar contact 36 of the relay iI AI-ID assuming its right-hand position,front contact 31 of this same relay, contact of the coder 15CTI4,

front contact I9 of the track code repeater relay l4--|'|FBP, backcontact |8 of the track .relay I4-I'IT, winding of the home-distantrelay HHD, front contact 38 of the approach homedistant relay I'IAHD,polar contact 39 of the relay I'IAHD assuming its right-hand positionand to the other terminal of said source of current. 7

Referring again to Fig; 1B of the drawings, as heretofore mentioned thedirectional stick relay i2S has a pick-up circuit including a frontcontact 30 of an approach track code repeater relay AISTP. It may bepointed out that this relay AI3TP is normally deenergized (track circuitunoccupied) because there is insufiicient current flowing in theapproach track relay AI3T to pick it up when there is no train. in theblock. The presence of a train in the block will, however, causeintermittent picking up of the approach track relay A! 3T causingintermittent application of energy to the approach track repeater relayAI3TP through the front contact M of the approach code following trackrelay AI3T. Since this approach track repeater relay AI 3TP is Shortcircuited by a rectifier, as conventionally shown, it will not drop awayduring the periods of intermittent deenergization of the approach trackrelay Ah'iT. In other words, the approach track repeater relay A! 3T? iscontinuously deenergized' where the directional stick relay is picked upby I the dropping of a track repeater relay, instead of the picking upof an approach track repeater relay, the contact in the pick-up circuitfor the stick relay has been designated 40 with an exponentcorresponding to the track relay with which it is associated.

Each of the track switches SwE, SwEB and S-wW is provided with adetector track circuit. The track relays for these detector trackcircuits have been designated DTE, lDTE-B and DTW, respectively. Byreferring to the detector track relay DTE (see Fig. 1A) it will be seenthat in addition to the contact HI already mentioned this track relay isprovided with front contacts 42 43 and The front contact 42 is includedin the circuits for controlling the home and I3HD cannot assume anenergized position unless both thedetector' track circuit including thetrack relay DTE and the track circuit including the track relay I3T areunoccupied. In a similarmanner the front contact 43 is included in theenergizing circuit for the home-distant relay |lHD,-so that thehome-distant relay l IHD cannot be picked up unless both the trackcircuit containing the track battery 13 and the detector track circuitcontaining the detector track relays DTE and DTEB are both unoccupied.The other contact is included in series with the front contact 45 of thetrack repeater relay l3FBP and these two contacts in series are capableof shunting the front contact 24 v of the directional stick relay IDS.These'front contacts M and 45 (see Fig. 1E) are effective to deenergizethe home-distant relay I8HD (see Fig. 1D) when there is a west-boundtrain in the section extending from signal S20 to signal S23(directional stick relay ZiiS deenergized and its contact 24 open) tocause the signal SIB to assume the stopposition and the signal SM toassume the caution position when a west-bound train passes the signalS23.

As heretofore pointed out the railway signaling systems such as shown inFigs. lA-lE are provided with wayside signals of the search-lightv typesuch as disclosed in the Field patent above referred to. Each of thesesignals includes a spectacle having color screens permitting theemission of green, yellow and red light respectively, this light beingemitted from an incandescent lamp. These lamps are normally deenergizedand are energized only upon the approach of atrain in the approach tracksection unless the signal is at stop. These incandescent lamps have beendesignated L with a uffix corresponding to the signal with which theyare associated and are each included in an energizing circuit containingan approach lighting contact 46 controlled by a back contact of a signalrepeaterv relay, and for convenience all of these contacts have beendesignated 46 with an exponent corresponding to the signal repeatingrelay with which they are associated. These relays GP and YGP are signalrepeating relays in that they. cannot assumean energized position whenthe associated signal is at stop. They, however, also perform anapproach lighting function in that .'.they will also be deenergized whena train'approaches the associated signal. The relay IZYGP is deenergizedupon picking up of approach repeater track relay AI3TP due to occupancyof the block extending from signal Sill to SIZ. Attention is directed tothe fact that dropping of either the signalrepeater relays IUYGP and'HGPwill light all of the three signal lamps LIB, LIOA, and LI 1. This isresorted to so that a train standing on the passing siding (non-trackcircuited) will have its signal lighted under all adverse trafficconditions. In other "words, these signal repeating relays GP and YGP attimes, by dropping, reflect the .ap proach of a train by lighting-thesignal and. at other times manifest that the signal i at stop-Obviously, the two ends of the passingsiding include the usual trackswitches, which are 'presumably hand operated in the present system,

relays IOHD and l3I-ID, respectively, and performs thesarme function inthese circuits that the front contact N3 of the --track repeater relayI3FBP performs. In other words,the home relays IOHD track switchwithwhich they are associated. .The

1 switch repeater contact 48 'is included in the reference charactershaving distinctive exponents corresponding to the track switches withwhich they are associated.

It willbe observed that the directional stick relay HIS is'provided withtwo pick-up circuits.

The one including the front contact 3| of the clear-caution signalrepeating relay. ISYGP and the other including the front contact 3 I ofthe clear-caution signal repeating relay IBAYGP and both including theback contact H of the detector track relay DTE. It will also be seenthat one stick circuit'for relay IDS includes back contact 40 and thestick contact 32 andthat another stick circuit. includes the backcontacts-40 31 and 3H of relays-ISFBP, ItYGP, and IUAYGP respectively.This circuit construction is resorted to in order to afforda pick-upcircuit for directional stick relay IOS irrespective. of whether thetrain entering the west end of the single track section illustratedmoves off of the main track or off of the side track of the passingsiding A. It will be noted that only one of signal repeating relays,vIQYGP or IIiAYGP can .be energized at a time and for this reason. frontcontact M and 3 I 10A have been provided in multiple for pick-,

ingu-p the directional stick relay "is. The directional stick relays ISSand S are similarly controlled by contacts identified by like referencecharacters having distinctive exponents.

Under normal conditions of the railway signaling system illustrated thetrack switche SwE, SwEB and SwW shownin Figs. IA, ID and 1E all assumetheir normal main track position. A- tention is directed to the factthat the detector track circuits associated with these track switchesare of the non-coded type, that is,.the.track relays arev continuouslyenergized so long a the detector track circuitsare notoccupied andassume their deenergized positions so longv as such detector trackcircuits are occupied. Each ofv the remaining track circuitsillustratedin Figs. l'A to 1E are coded atthe 75 impulse per minute. code rate andduring unoccupancy the track relaysof these track circuits pick up and,drop away seventy-five times during each. minute ofcunoccupancy. It willalso b'e'noted that all of the coded track circuits except the. trackcircuits between signals SM. and, SH: and betweentnsignals.

Sl 9 and S20 is provided with an approaclrtrack relay designated AT witha number between these letters each corresponding to'th'e prefixv of thetrack. relay with. which it is connected in. series. These approachtrack relays are normally deenergi'zed and are intermittent-1y energizedat the 75impulseper minute rate during occupancy of. the track circuitinlwhich they are included.

These approach track relay are. series relays and require a larger thannormal track circuit current to pick them up. It will be seen that theseapproach track relays are only'used for controlling signal repeaterrelays alsozcontrolled by signal mechanism contacts, andQirBctiOnaLstick; relays, and When soused conformtotheprinciple-ofthe nomesnormally closed circuit. It is considered perfectly safe to. controlthepicking up of a directional pick up results ina danger aspect insteadof a caution aspect; s

As just pointed' out the track circuits throug the single track sectionare coded at the. '75 impulse per minute code rate, but this is not done.for thepurpose of transmitting a special control over the'trackcircuititself, but is used primarily to provide a way of operatingcontacts at both ends of the track circuit intermittently andinsynchronism. 'In the system of Fig. 4 it is, however, used to transmitspecial controls. These contacts have been designated I8 and 20 in thedrawings. The contact 20 is a contact on a coding relay which'codes thetrack circuit, and the contact I8 is the contact on the track relay atthe opposite end of the track circuit which, of course, closely followsthe operation of the coding contact 25 located at the source end of thetrack circuit. It will readilybe seen that with the contacts I8 (seeFig. 1A) and 29 (see Fig. 1B) when both energized allow current to flowfrom right to left through this circuit to pick up the home-distantrelay IGHD from a source at the east end of the line circuit, and thatif these contacts I8 and 20 are both 'deenergized they allow current toflow from a source at the west end to pick up the horne distant relayI3HD. This alternate use; of the two line wires at a seventy-five timesperminute. rate is resorted to for controlling the home and distantrelays IUHD vand IBHD, and due to their slow-dropping char acteristicscauses these relays IElI-ID and It'll during clear or caution trafficconditions to be maintained continuously energized. In other words, theline circuit performs a double function inthat the contacts I8 and 20allow the .time

of useof this line circuit to be allotted alternately for the alternateenergization of these relays IilI-ID and IS'HD. What has been said inregard to the home-distant relays HEHD and ISHD is also true of all ofthe other home-distant relays and approach home-distant relays of Figs.lA -lE as well as of the mechanisms M of Figs. 4A-4E.

Fig. 1 operation.Let us now assume that there of the passing siding A'(see ,Figs. 1A and. 3A). The presence of this train will open thecircuit for the home-distant relay III-ID at a contact not shown in Fig.1A but shown in Fig. 1D and designated I8 of track repeater relay 2IFBP.With the home-distantrelay HHD deenergized the signal SH ,is put tostop, as shown by the letter R in Fig. 3A, because the circuit for thecontrol of its winding WII is open at front contacts #3 and I4 of therelay III-ID. With thesignal SII assumingv its stop position itscontacts 33 and 34 will assume a stop position as illustrated in thelowermost sketch of Fig. 2

changer contacts of the drawings, and when in such position the circuitfor the signal repeater relay ,IIGP is broken, thereby causing thisrelay IIGP to assume its retracted position and operate its pole- I'land 22 to the-reverse position, in which position the current throughthe winding of the home-distant relay I'3I-ID is reversed. so thatthepolar contacts I2 and I5 otthishome-distant relay ISHDJasSUme the left!hand position to cause the current flowing in the winding WI 3 of thissignal SI3 to be reversed thereby operating the signal SI3 to cautionposition in which it emits a yellow signal beam and operates thecontacts 33 and 34 to the lefthand or caution position (see Fig. 2) inwhich position the clear-caution relay I3YGP remains energized asbefore. In other words, movement of the signal SII to the stop positioncauses the signal SI3 to assume the caution position, but the nextsignal in the rear, namely, signal S" remains in its clear position.(see Fig. 3A). In other words, a train whether east-bound or westboundstanding on the main track of the passing siding A (see Fig. 1A) isprotected against a west-bound train moving in the single track sectionby a stop signal and a caution signal next in the rear thereof. 7

. The dropping of the signal repeating relay II GP, however, performsanother function, namely, the closing of its approach lighting backcontact 46 which results in' the illumination of the lamps LII LIIlA andLI I. These three lamps are controlled in multiple because it is desiredto illuminate the lamp LIIJA each time either the lamp LII] or LI! isenergized. It may be pointed out here that the lamp LIOA is notenergized with a train on the side track of the passing siding unlessthe associated track switch is in its take-siding position.v With thetrack switch SwE in the take-siding position theswitch box contactsMSwE' and SQSwE are both open placing the signals SIIJ and SH in thestop position but allowing signal SIIJA to reflect traflic conditionsahead and causing .deenergization of the signal repeater. relays IDYGPand II GP, which in turn cause the approach lighting contacts 46 and 46to be closed to approach light not only signal SIDA but also signalsSI!) and SI I.

Let us now assume that the east-bound train on the main track of thepassing siding A (see Fig, 1A) advances past the. clear signal SIII, asshown in Fig. 3B. The presence of this train on the detector. trackcircuit containing track relay DTE (see Fig-1A) causes this detectortrack relay DTE to assume its deenergized position.

Since this detector track relay DTE has a frontcontact 42 included inthe energizing circuit of the home-distant relay I3HD this, home-distantrelay I 3HD is deenergized, thereby deenergizing the winding WI3 of thesignal SI3 and operating this signal SI3 to its stop position. Movementof the signal SI3 to the stop position causes itscontacts 33 and 34 toassume their left-hand and their right-hand positions, respectively (seelowermost sketch of Fig. 2), thereby opening the circuit for the signalrepeater relay I3YGP causing deenergization of this relay. The droppingof the si nal repeater relay ISYGP at its back contact 45 closes anenergizing circuit for the lamp LI3 for the signal SI3, so that thissignal SI3 will actually emit a red beam signifying danger trafiieconditions to an opposing train. Furthermore, the dropping of the signalrepeater relay I3YGP causes operationv of the pole-changer contacts I1Z2 ,as a result of which the. energizing circuit for the approachhome-distant relay I'IAHD (see Fig. 1C) is broken because with thecontact 22 of the signal repeater relay. I3YGP in its retracted positionthe circuit for this approach home-distant relay I'IAHD is open at frontcontact 24 of. the directional stick relay I3S, this directional stickrelay only assuming its picked-up position in the event there is awest-bound train moving in the block between signals sis and SII. Withthe approach home-distant relay IIAHD now deen- 2) the caution-clearsignal repeater relay IIYGP- (see Fig. 10) also assumes its retractedposition and closes the signal lighting. back. contactMi for the lampLI'I of the signal SI'I. Furthermore, dropping of thesignal repeaterrelay I1YGP causes pole changing of its contacts I1 and 22 and since thefront contact 24 of the directional stick relay IIS is open theenergizing circuit for the home-distant relay IQHD is broken, therebycausing deenergization of the winding WI 9 for the signal SIS resultingin the placing offthe starting or head block signal SIS inthe stopposition. In this connection it should be'not ed that the energizing,circuit for the Winding WIS of the signal SIS includes a switchrepeating contact 48 and that if the track switch SwW assumed itstake-siding position this contact 48 would be opened but in this casethecontact 493 would be closed as a result of which the signal SISAinstead of signal SIB would have been controlled in accordance withtrafiic conditions in advance. Movement of the signal SIB to the stopposition causes the contacts 331? and 34 within the signal mechanism toassume the stop position as illustrated in I the lowermost. sketch in Fi2 and thereby cause the cautionclear repeater relay I 9YGPto assume itsretracted position. With the relay I BYGP in its retracted position theapproach lighting contact 46 is closed lighting up the lamps LIB, LI9.and LISA.

Also, with the signal repeating relay IBYGP in its retracted positionits pole-changer contacts 11 and 22 reverse the polarity of thecurrentapplied. to the home-distant relay ZIHD (see Fig; 1E). This is true eventhough the directional stick relay His is in itsnormal'retractedposition,

This is true because its front contact2 i of this stick relay is shuntedby a shunt circuit including the front contact M of the detector trackcupied. Should, however thetrain in question pass the opposing signalSll the signal SZI would be moved to its stop position by reason of.opening of thefrontcontactfi of the track repeater relay IBFBP (contact24 of relay I9S being open). With the signal S2I now assuming itscaution position because the home-distantrelay 2 IHD has been operatedtoits left-hand polar position (the trainunder consideration stilloccupying the position illustrated in Fig. 3B) and has pole changed thecurrent flow in the winding WZI, causes the signalSZI to assume thecaution position. This operation'of the mechanism. Of the signal SZI toits caution] position, in which both of its contacts 33 and 342 assumtheir Vii train past the signal Sltl .(see Figs. 1A and 33) causes .atumble down ofstop signals'to take place throughout theentire singletrack section resulting in the placing atstop of all of the opposing orwest-bound signals- Sl I, 313, Si! and SI9 and further results inputting the. signals S2! and S23 in the caution position. V

Another functionjthat takes place as the eastbound train passes the-signal SHlresides in the picking upof the directional stick relay ills.This j is accomplishedbythe closing of the pick-up circuit including theback contact MD ofthe de. tector relay and including the back contact s;'or the slow-dropping signal repeater relay 1 IOlAYGP, the frontcontact 3l .of the slow-dropping signal repeater relay IBYGB and thewinding for. this stick rela J'fiS. With the stick relay HlS onceenergized it is stuck up through a stick circuit including thebackcontact 48 of the detector track relay DTE and the stick contact :32inseries. H

As the east-bound train advances past the op- 1 posingsignal SI I (seeFig. 30) it results in continuous deenergization of the track relay I3T,which in turn results in con-tinueddeenergiza- ;tion or the home-distantrelay HJHD which was formerly deenergized by reasonof open contact 42 ofthe detector trackrelay DTE included in series in its energizingcircuit. With the track 1 relay I3' I' continuously deenergized thetrack re.- peater relays l3FP and I3FBP are continuously deener'gized..With the track repeater relay I3FBP in its'retracted position andwithits back con- ;tact 401 closed a supplemental stick circuit fortherdirectio'nal stick relay IDS i closed which stick -circuit includesthe back contact 49 of the track, repeater relay IBFBP, the backcontacts 3 and3l 10A of the signalrepeater relays tYGP and IUAYGP inseries, and the stick-contact 32 As the east-bound train underconsideration continues its movement between the signals SH and S12 (seeFig. 3C) the directional stick relay IGS will remain stuck up throughthe supplemental stick circuit heretofore traced, the original stickcircuit through back contact HI having been opened. Movement of theeast-bound train between the signals SH and SIZ as above pointed outresults in the intermittent picking up of the approach relay AIST whichin turn results in the repeater approach relay Ai3TP assuming itsenergized position continuously The front contact 39 of the approachrelay Al3'IfP now closes apic'k-up circuit for the di- .of, thisdirectional stick relay MS. Although thesignal SIZ had its mechanism inthe clear position under the assumed trailic condition underconsideration as illustrated in Fig. 3B,"this signal was then a darksignal, its associated approach li hting contact 46 of relay IZYGP beingopen.

With the train now advanced past opposing signal SH to a position asillustrated in Fig. 3C theapproach track relay AIBT is intermittent ypickedup to hold up repeater track relay AISTP continuously. Thisresults by Op 0f i back contact-i0 indropping of relay IZYGP and byclosing of back contact 46 in the lighting of sition'its frontclosedcontact 24 applie cauition energy through-a branch c rcuit in multiple.withthis'front contact M to the hornedistant relay next in the rear,-which is not shown ID of the drawings.

in Fig. 1A but1'has been designated IBHD in Fig; '1

rectional stick relay I25. This directional stick relay IZS is thenstuck up'through a stick circuit heretofore traced in connection withthe directional stick relay IDS. Also, the continuous picked-upcondition of approach repeater track relay AI3TP opens its back contact35 and drops the caution clear signal repeater relay I ZYGP and theclosure of its back contact 46 closes an energizing circuit for the lampLIZ.

:As the east-bound train now passes the signal SIZ (see Fig. 3D) it willresult in the continuous picking up of the approach repeater relayAIZTP. Since, however, the signal S|3 assumed its stopv Position, inview of the tumble-down which took place when the train passing signalSill, and its repeater relay I 3YGP assumed its retracted position thedirectional stick relay 138 is not picked up. The presence of this eastbound train in the track section between the signals SH and SM (see Fig.3D), however, results in continuous deenergization of the track relay121 which in turn results in continuous deenergization of the trackrepeater relay I2FP and IZFBP, so that the front contact I9 of the trackrepeater relay l ZFBP is opened thereby resulting in the continuousdeenergization of the home-distant relay I 2HD which in turn results inputting the signal SIZ in its stop position all for reasons heretoforepointed out. track repeater relay IZFBP' continuously deenergized theopening of its front contact 40 and deenergizatlon of the cautionclearrelay MYGP causes the approach lighting-contact 46 in the circuit forlamp M4 to be closed and the signal SM to become lighted as shown inFig. 333.

With the signal SI 2 in the stop position its caution-clear repeaterrelay IZYGP is deenererized. so that its approach lightin contact 46,is' closed to light the signal lamp L12 so longras the signal Sl2remains at stop and irrespective of the position assumed by the contact3!] of track repeater relay AlSTP. This dropping of the clear-caution sinal repeater relay IZYGP at its back contact 3! also closes asupplemental stick circuit for the directional stick relay 128. As soonas the rear end of the train passes the signal S12 (see Fig. 3D) thetrack relay IST will again intermittently respond to the coded currentapp-lied to the track circuit in which it is included y the contact 25of the coding relay, I3CPR. Intermittent picking up of the track relayI3T causes the track repeater relays I3FP and |3FBP to be held upcontinuously. The picking up of thislatter track repeater relay I 3FBPby the closing of its contact I9 allows caution current to flow to thehome-distant relay IIJHD through a circuit including the front contact24 of directional stick rela IZS, the front contact I 9 of relay ISFBPand the front contact 42 of the detector track relay DTE, as a result ofwhich the signal SID may assume the caution position. This Also, withthe

